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| 1 | /* | ||
| 2 | * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.io; | ||
| 27 | |||
| 28 | |||
| 29 | /** | ||
| 30 | * A character stream whose source is a string. | ||
| 31 | * | ||
| 32 | * @author Mark Reinhold | ||
| 33 | * @since JDK1.1 | ||
| 34 | */ | ||
| 35 | |||
| 36 | public class StringReader extends Reader { | ||
| 37 | |||
| 38 | private String str; | ||
| 39 | private int length; | ||
| 40 | private int next = 0; | ||
| 41 | private int mark = 0; | ||
| 42 | |||
| 43 | /** | ||
| 44 | * Creates a new string reader. | ||
| 45 | * | ||
| 46 | * @param s String providing the character stream. | ||
| 47 | */ | ||
| 48 | public StringReader(String s) { | ||
| 49 | this.str = s; | ||
| 50 | this.length = s.length(); | ||
| 51 | } | ||
| 52 | |||
| 53 | /** Check to make sure that the stream has not been closed */ | ||
| 54 | private void ensureOpen() throws IOException { | ||
| 55 | if (str == null) | ||
| 56 | throw new IOException("Stream closed"); | ||
| 57 | } | ||
| 58 | |||
| 59 | /** | ||
| 60 | * Reads a single character. | ||
| 61 | * | ||
| 62 | * @return The character read, or -1 if the end of the stream has been | ||
| 63 | * reached | ||
| 64 | * | ||
| 65 | * @exception IOException If an I/O error occurs | ||
| 66 | */ | ||
| 67 | public int read() throws IOException { | ||
| 68 | synchronized (lock) { | ||
| 69 | ensureOpen(); | ||
| 70 | if (next >= length) | ||
| 71 | return -1; | ||
| 72 | return str.charAt(next++); | ||
| 73 | } | ||
| 74 | } | ||
| 75 | |||
| 76 | /** | ||
| 77 | * Reads characters into a portion of an array. | ||
| 78 | * | ||
| 79 | * @param cbuf Destination buffer | ||
| 80 | * @param off Offset at which to start writing characters | ||
| 81 | * @param len Maximum number of characters to read | ||
| 82 | * | ||
| 83 | * @return The number of characters read, or -1 if the end of the | ||
| 84 | * stream has been reached | ||
| 85 | * | ||
| 86 | * @exception IOException If an I/O error occurs | ||
| 87 | */ | ||
| 88 | public int read(char cbuf[], int off, int len) throws IOException { | ||
| 89 | synchronized (lock) { | ||
| 90 | ensureOpen(); | ||
| 91 | if ((off < 0) || (off > cbuf.length) || (len < 0) || | ||
| 92 | ((off + len) > cbuf.length) || ((off + len) < 0)) { | ||
| 93 | throw new IndexOutOfBoundsException(); | ||
| 94 | } else if (len == 0) { | ||
| 95 | return 0; | ||
| 96 | } | ||
| 97 | if (next >= length) | ||
| 98 | return -1; | ||
| 99 | int n = Math.min(length - next, len); | ||
| 100 | str.getChars(next, next + n, cbuf, off); | ||
| 101 | next += n; | ||
| 102 | return n; | ||
| 103 | } | ||
| 104 | } | ||
| 105 | |||
| 106 | /** | ||
| 107 | * Skips the specified number of characters in the stream. Returns | ||
| 108 | * the number of characters that were skipped. | ||
| 109 | * | ||
| 110 | * <p>The <code>ns</code> parameter may be negative, even though the | ||
| 111 | * <code>skip</code> method of the {@link Reader} superclass throws | ||
| 112 | * an exception in this case. Negative values of <code>ns</code> cause the | ||
| 113 | * stream to skip backwards. Negative return values indicate a skip | ||
| 114 | * backwards. It is not possible to skip backwards past the beginning of | ||
| 115 | * the string. | ||
| 116 | * | ||
| 117 | * <p>If the entire string has been read or skipped, then this method has | ||
| 118 | * no effect and always returns 0. | ||
| 119 | * | ||
| 120 | * @exception IOException If an I/O error occurs | ||
| 121 | */ | ||
| 122 | public long skip(long ns) throws IOException { | ||
| 123 | synchronized (lock) { | ||
| 124 | ensureOpen(); | ||
| 125 | if (next >= length) | ||
| 126 | return 0; | ||
| 127 | // Bound skip by beginning and end of the source | ||
| 128 | long n = Math.min(length - next, ns); | ||
| 129 | n = Math.max(-next, n); | ||
| 130 | next += n; | ||
| 131 | return n; | ||
| 132 | } | ||
| 133 | } | ||
| 134 | |||
| 135 | /** | ||
| 136 | * Tells whether this stream is ready to be read. | ||
| 137 | * | ||
| 138 | * @return True if the next read() is guaranteed not to block for input | ||
| 139 | * | ||
| 140 | * @exception IOException If the stream is closed | ||
| 141 | */ | ||
| 142 | public boolean ready() throws IOException { | ||
| 143 | synchronized (lock) { | ||
| 144 | ensureOpen(); | ||
| 145 | return true; | ||
| 146 | } | ||
| 147 | } | ||
| 148 | |||
| 149 | /** | ||
| 150 | * Tells whether this stream supports the mark() operation, which it does. | ||
| 151 | */ | ||
| 152 | public boolean markSupported() { | ||
| 153 | return true; | ||
| 154 | } | ||
| 155 | |||
| 156 | /** | ||
| 157 | * Marks the present position in the stream. Subsequent calls to reset() | ||
| 158 | * will reposition the stream to this point. | ||
| 159 | * | ||
| 160 | * @param readAheadLimit Limit on the number of characters that may be | ||
| 161 | * read while still preserving the mark. Because | ||
| 162 | * the stream's input comes from a string, there | ||
| 163 | * is no actual limit, so this argument must not | ||
| 164 | * be negative, but is otherwise ignored. | ||
| 165 | * | ||
| 166 | * @exception IllegalArgumentException If readAheadLimit is < 0 | ||
| 167 | * @exception IOException If an I/O error occurs | ||
| 168 | */ | ||
| 169 | public void mark(int readAheadLimit) throws IOException { | ||
| 170 | if (readAheadLimit < 0){ | ||
| 171 | throw new IllegalArgumentException("Read-ahead limit < 0"); | ||
| 172 | } | ||
| 173 | synchronized (lock) { | ||
| 174 | ensureOpen(); | ||
| 175 | mark = next; | ||
| 176 | } | ||
| 177 | } | ||
| 178 | |||
| 179 | /** | ||
| 180 | * Resets the stream to the most recent mark, or to the beginning of the | ||
| 181 | * string if it has never been marked. | ||
| 182 | * | ||
| 183 | * @exception IOException If an I/O error occurs | ||
| 184 | */ | ||
| 185 | public void reset() throws IOException { | ||
| 186 | synchronized (lock) { | ||
| 187 | ensureOpen(); | ||
| 188 | next = mark; | ||
| 189 | } | ||
| 190 | } | ||
| 191 | |||
| 192 | /** | ||
| 193 | * Closes the stream and releases any system resources associated with | ||
| 194 | * it. Once the stream has been closed, further read(), | ||
| 195 | * ready(), mark(), or reset() invocations will throw an IOException. | ||
| 196 | * Closing a previously closed stream has no effect. | ||
| 197 | */ | ||
| 198 | public void close() { | ||
| 199 | str = null; | ||
| 200 | } | ||
| 201 | } | ||